An antireflection film is generally used as the outermost layer of a display of a display device, such as a cathode ray tube (CRT), a plasma display panel (PDP), an electroluminescence display (ELD) and a liquid crystal display (LCD), and has such a function that reduces reflectivity through the principal of optical interference to prevent decrease in contrast and mirroring of images due to reflection of outside light.
Such an antireflection film has been known that contains a transparent support having thereon a hard coat layer and a low refractive index layer. It has also been known that the refractive index of the low refractive index layer should be sufficiently low for reducing the reflectivity of the antireflection film.
For example, in an antireflection film containing triacetyl cellulose as a support and an UV cured film of dipentaerythritol hexaacrylate as a binder main component of a hard coat layer, the refractive index of the low refractive index layer is necessarily 1.40 or less for obtaining an average reflectivity in a wavelength range of from 450 to 650 nm of 1.6% or less. Examples of a material having a refractive index of 1.40 or less include magnesium fluoride and calcium fluoride as an inorganic substance, and a fluorine compound having a large fluorine content as an organic substance. However, only such a film that has poor scratch resistance can be obtained from these fluorine compound due to the poor cohesive power thereof, and thus, they are not suitable for a film disposed as the outermost layer of a display. In the case where a conventional compound improving scratch resistance is used to ensure sufficient scratch resistance, on the other hand, it brings about such a problem that the reflectivity is increased.
As described in the foregoing, there has been such a problem in that both low reflectivity and improved scratch resistance cannot be simultaneously realized.
In order to solve the problem, such a technique has been proposed that the refractive index of the hard coat layer is increased to reduce the reflectivity (as shown, for example, in JP-A-7-287102). However, the hard coat layer having a high refractive index has problems in that color heterogeneity occurs on the film due to the large difference in refractive index with respect to the support, and the wavelength dependency of the reflectivity also increased.
An antiglare antireflection film excellent in gas barrier property, antiglare property and antireflection property has been also proposed (for example, in JP-A-7-333404). However, it requires a silicon oxide film produced by CVD and thus is inferior in productivity in comparison to those produced by wet coating.
In order to improve scratch resistance of a film for the outermost layer, adhesion of the respective functional layers may be improved. For example, adhesion of a photosensitive resin composition is improved by containing (A) a binder polymer containing a carboxyl group, (B) a photopolymerization initiator and (C) an ethylene oxide adduct of a trimethylolpropane triacrylate (as shown, for example, in JP-A-7-56334), but further improvement is demanded in scratch resistance.